Animals and bugs were good, Lee wrote. But war was bad, along with global warming, pollution and international trade.

As for civilization?

The environmental militant who was killed Wednesday at the end of a tense hostage standoff at Discovery Communications headquarters in downtown Silver Spring, termed it "filth."

Lee, 43, who once threw money to bystanders as a protest along a Silver Spring street and who believed that the world would be better off without people, was shot by police after the almost four-hour standoff. Police have not publicly named Lee, but several local and federal law enforcement sources identified him as the gunman.

Lee held a grudge against Discovery, viewing the network as a purveyor of ideas he considered environmentally destructive and staging protests outside its headquarters, according to authorities and court records. Yet he got little farther than the lobby of the vast complex while the company alerted its thousands of employees and urged them to stay in locked offices and then evacuate using a designated stairwell.

Lee, whose environmental creed was spread across the Internet in manifestoes and blog posts, was killed at 4:48 p.m. after he stalked into the building with a handgun, took three hostages and later pointed his gun at one of them, said Montgomery County Police Chief J. Thomas Manger.

The incident, in the headquarters of the global television corporation just outside Washington, sent hundreds of employees streaming for safety into the afternoon heat without their purses, wallets and other personal items. It snarled traffic and riveted media audiences. Police said Lee had four makeshift explosive devices strapped to his body, and was wielding a gun. He entered the building about 1 p.m.

Police worked through the night searching the complex at Colesville Road and Georgia Avenue, trying to determine whether two backpacks and two boxes that seemed to have been carried into the building by Lee also were bombs.

Thursday morning, the building was given an all-clear, Montgomery County police said. Police spokeswoman Angela Cruz said officers were still at the complex, gathering evidence as part of their investigation.

About 1,900 people work at the Discovery building.

Cruz said Wayne Avenue remained closed to traffic Thursday morning between Ramsey Aveue and Georgia Avenue. Pedestrian access was restricted on the sidewalks on the Georgia and Wayne avenue sides of the Discovery building.